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5 Common Methods ofExamination forAnal Fistula
85
Womack anus function grading: Grade A: can
control any form of defecation; Grade B: unable
to control gas; Grade C: unable to control liquid
defecation and gas; Grade D: no control over
gases, liquids, or solids.
Kirwan anal function classication: Level I:
anal function well; Level II: unable to control
exhaust; Level III: accidental waste; Level IV:,
often waste; Level V: anal incontinence.Williams
standard: Grade A: good control of solids, liquids, and gases; Grade B: good solid and liquid
control, gas incontinence; Grade C: occasionally
a small amount of contaminated clothing, good
solid control, occasionally liquid incontinence;
Grade D: contaminated clothing, frequent uid
incontinence; Grade E: frequent solid and liquid
incontinence. A and B grades are considered
functional.
The rating scale is often regarded as too simple and only roughly evaluates the function of
anus. It has some shortcomings such as inconsistency, incompleteness, and inaccuracy, so it is
generally not recommended to use alone.
5.3.6.2 Total Score Evaluation Scale
The total score scale quanties the anal function
more objectively, specically, and effectively. It
can make up for the deciency of grade evaluation and is more widely used. The current total
score evaluation includes nine different evaluation methods. Rockwood, Hull, Wexner,
Pescatori, Vaizey, Skinner, Bai, Rothenberger,
and Lunniss all designed the total scores of their
respective teams. Nancy et al. systematically
summarized this. The score with the lowest total
score is 0–6, and the highest is 0–120.
The anal function scoring method of Wexner
(Table5.1) is a widely used anal function evaluation method in China.
There are four types of fecal incontinence: gas
incontinence, mucus incontinence, liquid incontinence, and solid incontinence. The severity and
frequency of fecal incontinence are different.
Therefore, the weight of different types of fecal
incontinence should be taken into account in the
total score evaluation. There are many ways to
allocate weights. At present, there are three main
ways to allocate weights: ① no weights are allocated; ② weight distribution; and ③ assign
weights according to the widely used objective
weight classication method.
The Jorge/Wexner Scale, Hull Scale, Valzey
Scale, and Lunniss Scale are not weighted, and
all types of fecal incontinence are considered to
have the same severity. The Jorge/Wexner Scale
is currently the most widely used scale without
weight assignment because of its simplicity, reliability, and sensitivity. However, since no weight
is assigned, the frequency of bowel movement
was signicantly affected by the subjective feelings of the subjects. Therefore, the Jorge/Wexner
Scale, while proving useful, does not reect the
true feelings of patients and thus limits its application to some extent.
Self-allocation of weights is better than no
allocation of weights, but it is not recommended
because the calculation method is cumbersome
and unscientic.
The Fecal Incontinence Severity Index (FISI)
designed by Rockwood etal. used an objective
weight allocation method. FISI consists of four
components: gas, mucus, liquid, and solid. It
contains six different frequency categories: two
or more times per day, once a day, twice a week
or more, once a week, one to three times a month,
and never. The total score is 0–61. While this
study helps us understand the importance of
weighting different types of fecal incontinence, it
will need to be replicated in other groups before
it can be widely used because of the small number of participants. However, FISI is recommended when fecal incontinence occurs
frequently. In addition, some scholars believe
that any method to evaluate anal function should
include tenesmus, as tenesmus is a common clinical symptom and has a great impact on patients’
quality of life. According to Lika etal.’s study,
the evaluation results of Wexner Scale, Vaizey
Scale, Pescatori Scale, and AMS Scale were consistent in the postoperative anal function measurement of patients with different anal
preservation methods and TNM stages, suggesting that the combined evaluation of the four
scales had a good consistency effect.
86
Table 5.1 Wexner anal function scoring method
Frequency
Incontinence
Dry stool 0 1 2 3 4
Loose stools 0 1 2 3 4
Gases 0 1 2 3 4
Need to pack 0 1 2 3 4
Lifestyle change 0 1 2 3 4
NB: never: 0; rarely: less than once a month; sometimes: more than once a month and less than once a week; often: more
than once a week but less than once a day; always: more than once a day. 0 is considered normal and 20 is considered
complete anal incontinence, with a low to high score representing the severity of anal incontinence
Never Rarely Sometimes Usually Always
R. Shi and L. Liu
5.3.7 Questionnaire Survey
onPatients’ Quality ofLife
The quality of life questionnaire survey of
patients can also indirectly reect the anal sphincter function; the disadvantage is that it is highly
subjective, so it is difcult to evaluate the anal
function objectively.
Quality of life questionnaire (FIQL) of fecal
incontinence was developed by the American
Society of Colon and Rectal Surgeons. ① It is a
specic quality of life questionnaire related to
defecation function. ② It deals with psychological coping/behavior (nine provisions). ③ It deals
with depression/self-perception (seven provisions). ④ It deals with embarrassment (three provisions). Feedback on each specic item has a
specic value, ranging from the ideal to worst
quality of life, and then the total score is calculated to indirectly assess changes in anal function. At present, FIQL is widely studied and has
certain practical value and certain validity and
sensitivity, so it is recommended for use.
Suggested Reading
1. Masahino Takano. Compiled by Shi Renjie. Essential
Diagnosis and Treatment of Anorectal Disease.
Beijing: Biomedical Branch of Chemical Press, 2009,
107–166.
2. Cao Jixun. Chinese Hemorrhoids and Fistula Science.
Chengdu: Sichuan Science and Technology Press,
2015, 37–64.
3. Huang Naijian. Anorectal Diseases in China. Jinan:
Shandong Science and Technology Publishing House,
1996, 735–742.
4. Zhu Rui, Zhang Pingsheng, Shen Lin, etal. Advances
in the diagnosis and treatment of anal stula.
Integrated Chinese and Western Medicine, 2011, 03
(3): 156–161, 166.
5. Shi Renjie, Gu Yunfei, Li Guonian, et al. 20 cases
of anal stula and perianal abscess examined by
transanal ultrasound. Chinese Journal of Anorectal
Disease. 2004, 24 (12). 28
6. Zhao Zehua, Li Ming, Wang Weizhong, et al.
Preoperative diagnostic value of body surface coil
magnetic resonance imaging for anal stula. Chinese
Journal of Medical Computer Imaging, 2007, 13 (6):
440–443.
7. Yang Bolin, Gu Yunfei, Zhuxin etal. Application of
magnetic resonance imaging in the diagnosis of complex anal stula. Chinese Journal of Gastrointestinal
Surgery, 2008,11(4): 339–342
8. Zhang Dewang, Li Xin, Tang Guangjian, et al. A
comparative study of preoperative MRI ndings
and surgical pathological ndings of anal stula.
Chinese Journal of Medical Imaging, 2014, 22 (6):
441–445.
9. Cao Liang, Yang Bolin. Progress in the application of
imaging examination in the diagnosis of anal stula.
Journal of Nanjing University of Traditional Chinese
Medicine, 2012, 28 (2): 198–200.
10. Wu Yanlan, Wang Yehuang. Research progress of
imaging examination in the diagnosis of anal stula.
Hebei Medicine, 2015, 37 (11): 1715–1717.
11. Feng Qunhu, Feng Guicheng, Lin Hongcheng et al.
Diagnostic value of multi-slice spiral CT in perianal
abscess and anal stula. Shanxi Medical Journal,
2014, (3): 346–347.
12. Ma Haifeng, Wang Song, Wang Xifu et al. A new
method for preoperative evaluation of anal stula:
clinical application of three-dimensional reconstruction technique of multi-slice spiral CT rectal tamponade stula angiography. Journal of Clinical Radiology,
2007, 26 (6): 605–608.
13. Li Wenru, Yuan Fen, Zhou Zhiyang and others.
Imaging diagnosis of anal stula in Crohn’s disease.
Chinese Journal of Gastrointestinal Surgery, 2014, 17
(3): 215–218
14. Guan Ruijian, Yuan Hanxiong, Ren Donglin. Bacterial
factors of perianal abscess and the relationship
between abscess and anal stula. Chinese Journal of
Integrated Traditional Chinese and Western Medicine
Surgery, 1996, 2 (6): 437–438.
5 Common Methods ofExamination forAnal Fistula
87
15. Wan Xingyang, Lin Xiaosong, Hubang etal. Clinical
signicance of preoperative colonoscopy for benign
anorectal diseases.Chinese Journal of Digestive
Surgery, 2014, 13(1): 47–50.
16. Zhang Bo, Wang Fan, Chen Wenping. Diagnostic
value of pelvic oor electromyography in outlet
obstructive constipation. Colorectal and Anal Surgery,
2007, 13 (2): 68–70.
17. Chen Jinping, Liu Baohua, Luo Donglin, et al.
Evaluation of electromyography in the diagnosis
of puborectalis syndrome. Journal of Chongqing
Medical University, 2007, 32 (11): 1185–1188,
1192.
18. Anorectal Surgery Group, Pediatric Surgery Branch,
Chinese Medical Association. Recommendation of
objective methods for the detection of anorectal function. Chinese Journal of Pediatric Surgery, 2011, 32
(8): 633–634
19. Wang Zhifeng, Ke Meiyun, Sun Xiaohong et al.
Anorectal Dynamics and Sensory Function in Patients
with Functional Constipation and Their Clinical
Signicance. Chinese Journal of Digestion, 2004, 24
(9): 526–529.
20. Huang Yan, Jin Xianqing, Li Xiaoqing, et al.
Signicance of endoanal ultrasound and anorectal manometry in the evaluation of anal function
after anorectal atresia surgery. Chongqing Medical
College, 2014, (28): 3704–3707, 3712
21. Gong Xiaoyong, Jin Zhiming, Zheng Qi, et al.
Progress in the evaluation of anal and rectal function
after low rectal cancer surgery. Shanghai Medical
College, 2010, 33 (11): 1057–1061.
22. Yin Wanbin, Zhao Xiaotang, Dai Lei, etal. Progress
in the study of anal sphincter function determination
methods. International Journal of Surgery, 2015, 42
(8): 567–570
Classication andDiagnosis
ofAnal Fistula
RenjieShi andJinHuiGu
6
Abstract
In ancient China, anal stulas were classied
by the location, shape, and characteristics.
According to the current classication method,
the anal stulas above the deep external anal
sphincter are dened as high anal stulas,
while those below the deep external anal
sphincter are dened as low anal stulas. The
anal stulas with relatively straight pipelines
and fewer than one inner opening/outer opening/pipelines are dened as simple, while
those with curved, more branches pipelines
and multiple external openings/internal openings/pipelines are dened as complex. Parks'
classication of anal stula and Yuyuko's classication of anal stula (Japan) are also widely
used in China. The diagnosis of the anal stula
is based on the symptoms, signs, and various
auxiliary examinations. It is important to
make good use of all kinds of examination
methods and to complete the colonoscopy and
anal function evaluation before operation.
Hidradenitis suppurativa, presacral cyst, and
other diseases are easy to be misdiagnosed as
anal stula, and attention should be paid to
prevent the errors.
Keywords
Anal stula · Diagnosis · Differential
diagnosis · Classication of diseases · Parks
Yukio Sumikoshi
6.1 Classication ofAnal Fistula
6.1.1 Classication ofAnal Fistula
inTraditional Chinese
Medicine
The classication of anal stula is complex.
Ancient Chinese physicians classied the stula
according to its location, shape, and
characteristics.
6.1.2 Classication ofAnal Fistula
inWestern Medicine
R. Shi (*)
Department of Anorectal Surgery, Afliated Hospital
of Nanjing University of Traditional Chinese
Medicine, Nanjing, Jiangsu, China
J. Gu
Suzhou Hospital of Traditional Chinese Medicine,
Afliated to Nanjing University of Chinese Medicine,
Suzhou, Jiangsu, China
© Chemical Industry Press 2021
R. Shi, L. Zheng (eds.), Diagnosis and Treatment of Anal Fistula,
https://doi.org/10.1007/978-981-16-5804-4_6
6.1.2.1 Classication ofAnal Fistula
Anal stula classication has been commonly
used in China since 1975. In July 2012, the
Guidelines for the Diagnosis and Treatment of
by theNational Conference
onAnorectal Surgery (1975)
89
90
R. Shi and J. Gu
Common Diseases in Anorectal Department of
Traditional Chinese Medicine was published by
the National Administration of Traditional
Chinese Medicine and still adopted mostly the
same classication methods. Although there were
slight differences in expression, the contents
were basically the same.
The distinction is marked by the deep line of
the external sphincter, the stula passing above
this line is deemed high, and the stula below this
line is deemed low. If there is only a single internal orice, the stula and external orice are
called simple. It is called complexed when there
are two or more internal orices, stulas, and
external orices. This classication is still widely
used in China.
Low Simple Anal Fistula
The internal orice is in the anal recess with only
one stula passing through the subcutaneous or
supercial part of the external sphincter, which
communicates with the skin.
Low Complex Anal Fistula
There are more than two internal or external
orices, and the stula is located in the subcutaneous or supercial part of the external
sphincter.
High Simple Anal Fistula
The internal orice is in the anal recess, with only
one stula, which runs above the deep layer of
the external sphincter.
High Complex Anal Fistula
There are more than two external orices connected with the internal orice through the stula or with a branch cavity. The main stula
passes through the deep layer of the external
sphincter.
6.1.2.2 Parks 4 Class Method (1976)
According to the relationship between the stula
and sphincter, anal stula can be divided into
four categories (Fig.6.1). This is the main anal
stula classication method most commonly
used abroad.
Intersphincter Fistula (Low Anal Fistula)
This is most common, accounting for about 70%
of cases, and is the result of perianal abscess. The
stula passes only through the internal sphincter.
There is usually only one external orice, which
is close to the anal margin, about 3–5cm. A few
stulas go upward, forming a blind end between
the rectal circular muscle and the longitudinal
muscle or penetrating the rectum to form a high
sphincter stula.
Transsphincter Anal Fistula (Low or High Anal Fistula)
Accounting for about 25% of cases, it is the result
of abscess in the ischiorectal fossa. The stula
passes through the supercial and deep parts of
the internal and external sphincters. There are
often several external orices and branches communicating with each other. The external orice
is about 5cm away from the anal margin. A few
stulas pass upward through the levator ani muscle to rectal connective tissue, forming a pelvicrectal stula.
Superior Sphincter Anal Fistula (High Anal Fistula)
This is rare, accounting for about 5% of cases.
The stula goes up through the levator ani muscle, then down to the ischiorectal fossa and penetrates the skin. Because this type of stula often
involves the anal and rectal rings, it is difcult to
treat, and it often requires staging an operation.
External Anal Fistula ofSphincter (High
Anal Fistula)
This is rarest, accounting for only about 1% of
cases, and is the result of pelvic and rectal space
abscess combined with ischiorectal fossa abscess.
The stula passes through the levator ani muscle
and connects directly to the rectum. This type of
anal stula is often caused by Crohn's disease,
intestinal cancer, or trauma. Treatment should
therefore pay attention to the primary focus.
Marks and Ritchie (1977) pointed out that the
clinical manifestations of sphincter stula were
simple, while the last three types of anal stula
had a long history, more rounds of operation and
ab
c. Suprasphincteric d. extrasphincteric
Internal Anal
6 Classication andDiagnosis ofAnal Fistula
Fig. 6.1 Classication
of stula-in-ano (Parks)
cd
91
a. Intersphincteric b. transsphincteric
abscess drainage, more horseshoe type or spread,
and more lateral and multiple external orices.
Levator Ani M.
6.1.2.3 Yukio Sumikoshi’s
Classication ofAnal Fistula
In 1972, Japanese scholar Yukio Sumikoshi put
IV
forward the anal stula classication method
based on the relationship between anal stula and
sphincters (Fig. 6.2). This method is widely
respected and applied in Japan and is basically
the national anal stula classication method in
Japan. Japan's renowned anorectologist Masahino
Takano said that, except for a few special cases of
mutation, the method is based on anatomical for-
External Anal
Sphincter
III
mulation, strong theories, clinical practice, and
very practical classication. Taka Utui also commented that “among all the classication methods, only Yukio Sumikoshi's classication can
Fig. 6.2 Classication of stula-in-ano (Yukio
Sumikoshi)
HH
I
II
L
L
Sphincter
92
R. Shi and J. Gu
fully display the three-dimensional shape and
straightforwardly show the location, direction
and complexity of anal stula.”
The anal stula was classied into four categories in Yukio Sumikoshi's classication method
and then divided into 11 subcategories, which
were shown by marks and easy to remember.
Based on the internal and external sphincters and
levator ani muscles, the gap between the mucosa
or anal epithelium and the internal sphincter is
marked as I, the gap between the internal and
external sphincters is marked as II, the gap under
the levator ani is marked as III, and the gap above
the levator ani is marked as IV.Traveling below
the dental line is marked as L, and traveling
above the dental line is marked as H.Those that
walk on one side are represented by U (unilateral), while those that walk on both sides are represented by B (bilateral). Simple stula and
complicated stula are called S (simple) and C
(complicated) (Table6.1).
According to the relationship between the
abscess and sphincter and according to the Yukio
Sumikoshi’s classication of anal stula
(Fig. 6.3), Masahiro Takano divided perianal
abscesses into six categories: subcutaneous
abscess, submucosal abscess, low intermuscular
abscess, high intermuscular abscess, sciatorectal
fossa abscess, and pelvic and rectal fossa abscess.
The forms I LA, II HA, II LA, III A, and IVA
were used, respectively. A is an abbreviation for
abscess.
Table 6.1 Yukio Sumikoshi’s classication of anal
stula
I.Subcutaneous or submucosal stula Mark
L subcutaneous stula
H submucosal stula
II.Intersphincteric stula
L low intersphincteric………S simple
………………C complicated
H high intersphincteric………S simple
………………C complicated
III.Infralevator stula
U unilateral………S simple
………………C complicated
B bilateral………S simple
…………………C complicated
IV.Supralevator stula IV
I L
I H
II Ls
II Lc
III Us
III Uc
III Us
III Uc
III Bs
III Bc
6.1.2.4 Other Taxonomies
Classication ofFistulas Based onInternal
andExternal Characteristics
1. Single-Orice Internal Fistula
This is also known as internal blind stula,
where only the internal orice communicates
with the stula, and there is no external
orice.
2. Internal and External Fistula
This is the most common type of anal s-
tula. The stula has both internal and external
orices. The external orice is on the surface,
and the internal orice is usually in the anal
sinus. The internal and external orices are
connected by the stula.
3. Single-Orice External Fistula
This is also known as the external blind s-
tula. Only the external orice is connected to
the stula, but there is no internal orice. This
type of anal stula is rarely seen clinically.
4. Total External Fistula
The stula has more than two external
openings, which are connected to each other
by pipelines without an internal orice. This
kind of anal stula is also rare in the clinic.
Classication ofFistulas Based
ontheShape ofAnal Fistulas
1. Straight Fistula
The stula is straight, and the internal and
external orices are in the same direction. It is
more common in the clinic, accounting for
more than 1/3 of cases.
2. Curved Fistula
The stula is curved in path, and the inter-
nal and external orices are mostly not in the
same direction.
3. Posterior Horseshoe-Shaped Anal Fistula
The fistula is curved and shoe-shaped,
in the posterior position of the anus, with
the inner orifice in the middle of the
posterior.
4. Anterior Horseshoe-Shaped Anal Fistula
The stula is curved and shoe-shaped,
which is relatively rare, and is in front of the
anus.
External Anal
Sphincter (Deep)
ILA
IIHA
IVA
6 Classication andDiagnosis ofAnal Fistula
Levator Ani M.
External Anal Sphincter
(Subcutaneous)
External Anal Sphincter
(Subcutaneous)
Internal Anal Sphincter
93
IHA
IIIA
IILA
Fig. 6.3 Classication of perianal abscess. According to
the classication of anal stula, it is divided into subcutaneous abscess (ILA), submucosal abscess (IHA), low
intermuscular abscess (III LA), high intermuscular
5. Circumferential Fistula
Classication ofFistulas Based
ontheRelationship Between theFistula
andtheSphincter
1. Subcutaneous Fistula
2. Submucosal Fistula
3. Fistula Between Supercial External
4. Fistula Between Deep and Supercial
5. Deep Fistula Between the Levator Ani and
6. Superior Levator Anal Fistula
The stula surrounds the anal canal or rectum, and operation on it is difcult and
complicated.
In the anal subcutaneous layer, shallow,
low position.
Under the rectal mucosa, not on the surface
of the body.
Sphincter and Subcutaneous Part
External Sphincter
External Sphincter
abscess (IIHA), ischiorectal fossa abscess (IIIA), pelvic
rectum Abscess (IVA) type 6. A is the abbreviation of
Abscess
Classication ofFistulas Based
ontheNumber ofInternal andExternal
Orices andFistulas
1. Simple Anal Fistula
There is only one internal orice, one
external orice, and only one stula connecting the internal and external orices.
2. Complex Anal Fistula
There are two or more internal orices or
external orices, more than two stulas, or
branches and blind canals.
Classication ofFistulas Based
ontheEtiology andPathological Nature
ofAnal Fistulas
1. Nonspecic Anal Fistula
The mixed infection of Escherichia coli,
Staphylococcus, Streptococcus, and so on
usually causes anorectal abscess and forms
anal stula after ulceration. This is most common in the clinic.
94
R. Shi and J. Gu
2. Specic Anal Fistula
This includes tuberculous anal stula,
Crohn's disease anal stula, and so on.
Eisenhammer: Three Categories andFive
Types Method (1966)
Eisenhammer divided anal stulas into the internal group, external group, and internal and external combined group according to the theory of
intramuscular stula abscess.
1. Internal Group
Refers to the intramuscular stula abscess
and submucosal stula originating from the
anal recess inside the anal canal. There are three
types of stulas here: high internal and external
sphincter stula, low internal and external
sphincter stula, and submucosal stula.
2. Outside Group
Refers to infectious stula abscess of non-
anal recess gland originating from outside the
anal canal, such as ischiorectal fossa abscess
caused by hemorrhagic infection, trauma, etc.
The outside group can be further divided into
two types: (1) ischiorectal fossa stula and (2)
subcutaneous stula.
3. Internal and External Merger Group
Refers to the irregular type of infection
originating from both sides of the anal canal,
and this happens in many cases.
Goligher’s Classication (1975)
The Goligher taxonomy was developed on the
basis of the Milligan–Morgan taxonomy. It is
divided into the following:
1. Subcutaneous Anal Fistula
This accounts for 10%–15% of cases. The
stula is located in the lower part of the perianal skin, and the internal orice is at the dental line. Sometimes it can be presented as blind
subcutaneous external stula (sinus tract).
2. Low Anal Fistula
This is most common, accounting for
60%–70% of cases. The stula passes through
the subcutaneous part of the external sphincter or the inferior edge of the internal sphincter. The internal orice is often near the dental
line; sometimes it can be a blind external stula (sinus tract).
3. High Anal Fistula
This accounts for 15% of cases, and the s-
tula location is higher, close to the anal rectal
ring, but not over this ring. The internal orice
is often near the dental line. The stula can
pass through the internal and external sphincters and become oblique. Sometimes there is
no internal orice, showing a high blind external stula.
4. Anorectal Fistula
Clinically relatively rare, this accounts for
about 5% of cases, and there are two types.
One is the ischiorectal fossa type. The stula is
under the levator ani muscle. Because the levator ani muscle is oblique, the stula begins
above the anorectal ring. The internal orice
can be single or multiple, often under the anorectal ring. The other is pelvic-rectal type with
stula above the levator ani muscle. The internal orice may be under or above the anorectal
ring, or it may be an external stula of the blind
end. The stula is not connected with the rectum. Goligher believes that the internal orice
above the anal and rectal ring is often caused
by articial causes, such as inappropriate probe
examination, articial internal orice, or by
incorrect incision of pelvic and rectal space
abscess or ischiorectal fossa abscess.
5. High Intermuscular Anal Fistula
This is rare in the clinic. It is usually the
blind sinus tract, extending upward from the
dental line. The stula is between the circular
and longitudinal muscles. Sometimes it can
be under the mucosa, and the skin has no
external orice. Sometimes it appears as an
internal stula.
6.2 Diagnosis ofAnal Fistula
6.2.1 Diagnostic Methods ofAnal
Fistula
Diagnosis of anal stula is not difcult. According
to the history of intermittent onset of anal swelling and pain and purulence, combined with the
6 Classication andDiagnosis ofAnal Fistula
95
symptoms of swelling and pain, purulence and
other characteristics, and then according to an
anorectal specialist examination, such as the
detection of an external orice, stula, internal
orice, or other characteristic changes, anal stula can be diagnosed. After the diagnosis of anal
stula, it is necessary to further clarify the location of the internal orice of the anal stula,
whether the anal stula is simple or complex,
whether it is high or low, and the shape of the
stula, the relationship between the stula and
the sphincter, etc.
Generally, simple anal stula has only one
external orice, one internal orice, and one stula, while complex anal stula can form multiple branches, which connect to the external
orice and the internal orice. However, some
people believe that complex anal stula should
not be divided into the number of external orices because sometimes the anal stula has multiple external orices but treatment is not difcult.
The main pipeline affects anorectal ring or above
anorectal ring. Although there may be only one
external mouth and one internal mouth, it is difcult to treat, so it should be a complex anal
stula.
As for the classication of high and low anal
stulas, Parks’s method (1967) has been widely
used in clinical practice to classify high and low
anal stulas based on whether the stula crosses
the highest self-control muscular layer. He
dened high anal stula as “an anal stula in
which a stula passes over the top of the highest
self-control muscle.” If the stula passes through
the levator ani muscle (mainly the puborectal
muscle), it is a high anal stula, and the lower
anal stula is the anal stula below the levator ani
muscle. Milligan–Morgan (1934) referred to stula as high anal stula if it is above the dental
line level and as low anal stula if it is below the
dental line level.
The shape of the stula can be a straight stula, curved stula, and horseshoe stula. The
external and internal orices of the straight stula
are in corresponding positions, and the pipes are
straight or slightly curved, often shorter. Straight
stulas can be low or high. Straight stulas also
have more than one line, or near one line, which
is relatively easy to treat. The external and internal orices of the curved stula are often not in
the same direction, and the curved condition can
be quite different. Some have a very small curvature, whereas some have a very large curvature.
Horseshoe-shaped anal stula is mostly posterior
horseshoe-shaped. Generally, the internal orice
is in the posterior, and the stula is shoe-shaped
behind the anus. Occasionally, there are anterior
horseshoe anal stulas and even whole horseshoe
anal stulas.
The nature of anal stula should also be claried in the diagnosis of anal stula. General anal
stula refers to the anal stula caused by common intestinal or dermatogenic bacterial infections and accompanied by noninammatory
bowel diseases. Specic anal stula refers to
tuberculous anal stula and anal stula complicated by Crohn's disease.
In the diagnosis of anal stula, a comprehensive examination should be carried out on the
basis of a detailed collection of medical history in
order to determine the general situation and know
whether the patient has diabetes, leukemia,
Crohn's disease, ulcerative colitis, or other diseases and whether there are any surgical contraindications. This is important for treatment
decision-making and the choice of treatment
methods.
In addition, according to the clinical symptoms and signs, the duration of anal stula should
be determined as static, chronic active, or acute
inammation. These are also closely related to
the choice of appropriate treatment methods.
6.2.2 The Importance
ofPreoperative Diagnosis
ofAnal Fistula
Preliminary diagnosis of anal stula is not difcult, but for some high complex anal stulas, it is
still difcult to accurately know the number of
stulas, distribution, direction, and location of
the internal orice before operation. Precise preoperative diagnosis is of great signicance in
making an operative plan, reducing variability
and randomness during operation, improving the